Mechanism for moving a printing head in a printer

ABSTRACT

Mechanism for moving a printing head in a printer. The printing head is mounted on a head holder movable between a start position and a terminal position for the printing operation and the head holder is urged by a spring toward the start position. A winding drum is driven by an electromagnetic clutch through reduction gearing and the clutch is in turn releasably driven by an electric motor through a control circuit adapted to supply a signal to the clutch to release the same. An endless belt is stretched around the winding drum and pulley means so as to be driven by the drum. A portion of the wire stretched between the pulley means extends in parallel and close to the path of movement of the head holder and a portion on that portion of the wire is secured to the head holder so as to move the same with the movement of the wire. A detecting coil is operably coupled with the electro magnetic clutch and connected to the control circuit so that, when the clutch drives the head holder to the terminal position through the drum and the wire, the signal for releasing the clutch is generated so as to release the clutch thereby moving the head holder to the start position by the action of the spring. A switch is provided near the start position and connected to the control circuit so that, when the head holder reaches the start position, the switch is actuated to actuate the electro-magnetic clutch through the control circuit thereby moving the head holder toward the terminal position for the printing operation of the printing head.

[11 3,814,230 June 4,1974

MECHANISM FOR MOVING A PRINTING HEAD IN A PRINTER Primary ExaminerRobert E. Pulfrey Assistant Examiner--Eugene H. Eickholt Attorney, Agent, or Firm-Hans Berman [75] Inventor:

Katsuhiko Okabe, Tokorozawa, Japan Assignee: Kabushikikaisha C'opal,

Tokyo,

492a 1 Mechanism for moving a printing head in a printer. Mar. 22, 1973 The printing head is mounted on a head holder movable between a start position and a terminal position [21] App]. No.: 343,640

for the printing operation and the head holder is urged by a spring toward the start position. A winding drum [30] Data Apr. 18, I972 F r ign App n Priority g is driven by an electromagnetic clutch through reduc- 47. 45904 tion gearing and the clutch is in turn releasably driven A 28, 1912 Japan ,474%5905 by an electric motor through a control circuit adapted to supply a signal to the clutch to release the same. An

[52] US. endless belt is stretched around the winding drum and [51] Int. B4lj 19/00' pulley-means so as to be driven by the drum. A por- [58] Field of Search 197/1 R, 48, 49, 60, 65, tion of the wire stretched between the pulley means extends in parallel and close to the path of movement of the head holder and a portion on that portion of the [56] References Cited wire is secured to the head holder so as to move the UNITED STATES PATENTS same with the movement of the wire. A detecting coil is operably coupled with the electro magnetic clutch and connected-to the control circuit so that, when the clutch drives the head holder to the terminal position through the drum and the wire, the signal for releasing the clutch is generated so as to release the clutch thereby moving the head holder to the start position by the action of the spring. A switch is provided near the start position and connected to the control circuit so that, when the head holder reaches the start position, the switch is actuated to actuate the electromagnetic clutch through the control circuit thereby moving the head holder toward the terminal position for the printing operation of the printing head.

2 Claims, 1 Drawing Figure .ll-ll Wusteney et a1. 4 Howard uu unu lu n n finnfl U .ke ur n e v n" S m nhnmkma um a uhoiesn e .n nk m c l n rat a a o a m ecoro a r BCBSMPSCBLMKWGW 9258900 226 .3333 56666777777777777 0 9999999999999999 llllltllillllllllllllll '1 MECHANISM FOR MOVING A PRINTING HEAD IN A PRINTER BACKGROUND OF THE INVENTION The present invention relates to a mechanism for moving a printing head in a printer.

In a prior art printers such as so-called non-impact printers using printing heads of the therrnosensitive 'type, varioustypes of mechanisms have been developed to move the printing head holder in a printer for the printing operation, including the types such as those manufactured by Friden, Inc., Ing. C. Olivetti & C., S.p.A. and Hewlett-Packard Co. All of these types utilize a feed shaft provided with a helical groove, and a pin secured to the head holder movable in parallel to the feed shaft guided by a guide bar or guide bars is engaged with the groove so that the head holder is moved axially of the guide bar as the feed shaft rotates. Such a construction is complicated and is expensive in manufacture and requires high accuracy of the parts to be assembled thereby making the cost very high.

SUMMARY OF THE INVENTION a novel and useful device for preventing excessive movement of the printing head in a printer which might result in injury of the printer.

The above object is achieved in accordance with the present invention by the provision of a mechanism for moving a printing head mounted on a head holder of a printer movable between the start position and the terminal position for the printing operation, the printer having a control circuit for supplying'printing signals to the printer in accordance with the demand for the printing operation, an electric motor for driving the head holder, the mechanism being characterized by a spring attached to the head holder and the printer frame for urging the head holder toward the start position, an electromagnetic clutch operably coupled with the electric motor and connected to the control circuit, the electromagnetic being released upon receipt of a signal from the control circuit, a winding drum, a reduction gear connecting the winding drum to the electromagnetic clutch so as to drive the drum at a reduced speed with respect to the speed of the latter, a plurality of pulleys rotably mounted on the printer frame, an endless wire stretched around the winding drum and the plurality of pulleys with a point on the wire secured to the periphery of the drum so as to be driven thereby, the pulleys being so arranged that a portion of the wire stretched around the adjacent two pulleys extends in parallel and close to the path of movement of the head holder, a point on that portion of the wire being secured to the head holder so as to move the head holder together with the movement of the wire toward the terminal position against the action of the spring when the electromagnetic clutch is actuated, a detecting coil operably interrelated with the electromagnetic clutch and connected to the control circuit, the detecting coil being so located in relation to the actuation of the electromagneticclutch as to generate the signal for releasing the electromagnetic clutch when the head holder is moved to the terminal position by the action of the electromagnetic clutch thereby moving the head holder toward the start position by the action of the spring, and a switch connected to the control circuit and so positioned that it is actuated when the head holder reaches the start position so as to actuate the electromagnetic clutch through the control circuit.

In accordance with the present invention, since the electromagnetic clutch is coupled with the winding drum through the reduction gear, the electromagnetic clutch may be driven at a high speed, so that the required torque thereof may be made small there by permitting an electromagnetic clutch of a small capacity can be utilized while the time lag is made very small thus increasing the accuracy in operation.

In accordance with a further feature of the present invention, a normally closed leaf switch is provided adjacent to the terminal position of the head holder and connected in series to the electromagnetic clutch and the control circuit. The normally closed switch is so located that it abuts against the head holder when the same reaches the terminal position so that the switch is opened to release the electromagnetic clutch so as to positively prevent the head holder from moving beyond the terminal position regardless of the false function of the control circuit. I

BRIEF DESCRIPTION OF THE DRAWING The accompanying drawing is a perspective view showing the internal construction of the printer of the present invention with the casing removed for the illustration purpose.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The printer of the present invention shown in the accompanying drawing comprises a machine frame 19 mounting thereon an electric driving motor 1. A main shaft 3 is rotatably mounted on the frame 19. A belt 5 is stretched around a pulley 2 mounted on the drive shaft of the motor 1 and a pulley 4 mounted on the main shaft 3 so that the main shaft 3 is driven by the driving motor 1.

A pinion 6 is secured to the main shaft 3 as shown and the pinion 6 is coupled with the input gear 8 of an electromagnetic clutch 7 mounted on the frame 19 so as to drive the clutch 7 by the main shaft 3. A gear 9 and a pinion 10 are secured to the output side 7a of the electromagnetic clutch 7 so that rotational driving force is transmitted to the gear 9 and the pinion 10 from the main shaft 3 through the engagement of the gears 6and 8 when the electromagnetic clutch 7 is electrically energized, while the output side and, hence the gear 9 and the pinion 10 are made free to rotate relative to the main shaft 3 when the clutch 7 is electrically deenergized or released.

The gear 9 is engaged with a pinion ll rotatably mounted on the frame 19 and the pinion ll mounts thereon a toothed printing signal sensing disc 12 having a plurality of sensing teeth formed in the periphery thereof and a head holder stopping signal sensing disc 13 having a sensing tooth formed in the periphery thereof so that the discs 12 and 13 are rotated when the clutch 7 is electrically energized or actuated.

I A printing signal detecting coil 14 is located adjacent to the printing signal sensing disc 12 so as to cooperate therewith so that the coil 14 is actuated each time the respective sensing teeth formed in the periphery of the disc 12 pass across the coil 14 thereby supplying printing signals to a control circuit (not shown) of the printer connected to the coil 14 so that the printing operation is effected 'by aprinting head to be described below. The control circuit per se is well known in the art so that detailed description thereof is not given here.

Similarly, a head holder stopping signal detecting coil 15 is located adjacent to the head holder stopping signal sensing disc 13 so as to cooperate therewith so that the coil 15 is actuated each time the sensing tooth passes across the coil 15. The coil 15 is connected to as shown. Thus, when the electromagnetic clutch 7 is actuated or electrically energized, the drum 16 is driven by the clutch-7 at a reduced rotational speed with respect to that of the output side 7a of the clutch 7. In other words, the electromagnetic clutch 7 may be rotated at a higher speed in comparison with the rotational speed of the drum 16 required for the proper operation of a head holder 18 as described below. 4

The head holder 18 is slidably mounted on a guide bar 20 the both ends of which are secured to the frame 19 so that the head holder 18 is movable between the start position and the terminal position for the printing operation. The head holder 18 swingably mounts I thereon a printing head 21.

An electromagnet 22' is arranged in the frame 19 and a bracket 25 is swingably supported on a supporting bar 24 the both ends of which are secured to the frame 19. A head, biasing bar 23 cooperating with the printing head 21, is mounted on the bracket 25. The head biashead 21 is urged against the sheetto be printed at an appropriate pressure for the printing operation.

The sheet to be printed is fed in the well known manner by means of sheet feeding magnet 28, sheet feeding shaft 29 and sheet feeding spring clutch 291': so as to permit the printing operation to be effected by the printer.

An end 26a of a helically wound coil spring 26 is secured to the head holder 18 and the spring 26 extends in parallel to the guide bar 20 and around an idler pulley 27 rotatably mounted on one side of the frame 19 and back toward the other side of the frame 19 where the other end of the spring 26 is secured as shown so that the head holder 18 is urged by the spring 26 toward the start position for the printing operation.

An idler pulley 30 is rotatably mounted adjacent to the above mentioned one side of the frame 19 while a pair of idler pulleys 31, 32 are rotatably mounted on the otherside of the frame 19. A wire 33 is stretched around the winding drum l6,'the pulley 31, the pulley 30 and the pulley 32.

A point on the wire 33 is secured to the periphery of the drum'l6 so as to forcibly drive the wire 33 by the drum 16.

The pulley 31 and the pulley 30 are so positioned that the portion of the wire 33 stretched therebetween'extends in parallel to the guide bar 20 adjacent to the head holder 18. A portion 33a of that portion of the wire 33 stretched between the pulley 30 and the pulley 31 is fixedly secured to the head holder 18 so as to positively drive the head holder 18 by the wire 33.

' A damper 34 for cushioning and absorbing the shock of the movement of the head holder 18 toward the start position effected by the spring 26 is provided in the frame 19.

A switch (not shown) is provided on the previously mentioned one side of the frame 19 and connected to the control circuitThe switch is so positioned in relation to the head holder 18 that it is actuated by the head holder 18 when it reaches the start position for the printing operation by the action of the spring 26 so that the electromagnetic clutch 7 is energized through the control circuit so as to actuate the output side 7a thereof and, hence, the gear 9 and the pinion 10, thereby driving the winding drum 16 soas to move the head holder 18 against the action of the spring 26 from the start position toward the terminal position through the wire 33, while the printing signal sensing disc 12 and the head holder stopping signal sensing disc 13 are rotated through the gear 9 and the pinion ll engaging therewith in timed relation to the rotation of the winding drum 16 and, hence, the movement of the head holder 18 toward the terminal position for the printing operation.

The head holder stopping signal sensing disc 13 is so arranged in relation to the head holder stopping signal detecting coil '15 that the coil 15 is actuated when the head holder 18 reaches the terminal position, so that a signal is supplied from'the coil 15 to the control circuit for releasing or deenergizing the electromagnetic clutch 7 thereby freeing the winding drum 16 so as-to permit the head holder 18 to return from the terminal position toward the start position by. the action of the spring 26 with the damper 34 effecting the cushioning action at the end of the movement of the headholder 18. When the head holder 18 reaches the start position, the switch for initiating the movement of the head holder 18 toward the terminal position is actuated as described previously, and the sequence of the above operations is repeated during the printing operation.

The printing signal sensing disc 12 is so positioned in relation to the printing signal detecting coil 14 that printing signals are successively supplied from the coil 14 to the control circuit during the time the head holder 18 is moving from the start position toward the can be made simple while exact operation of the printer is insured and the adjustment is made easy.

In accordance with a further feature of the present invention, a-normally closed leaf switch 35 comprising a leaf contact 35a and a leaf contact 35b normally held in contact with the leaf contact 350 is provided in the frame 19 adjacent to the terminal position of the head holder 18. The switch 35 is connected in series to the electromagnet 7 and the control circuit. The head holder 18 is provided with a projection 18a secured thereto. The projection 18a is so positioned in relation to the switch 35 that the projection 18a abuts against the leaf contact 35aof the switch 35 so as to move the leaf contact 35a apart from the leaf contact 35b when the head holder 18 has just reached the terminal position so as to open the switch 35.

Thus, the electromagnetic clutch 7 is positively released by the opening of the switch 35 when the head holder 18 reaches the terminal position even though false function of the detecting coil or sensing disc 13 will take place, thereby positively preventing the head holder 18 from moving beyond the terminal position causing damage to the printer.

In the present invention, a thermally sensitive printing head, an electronic printing head or an ink jet printing head can be used as the non-impact printer. However, a mechanical printing hammer can be used in place of the above mentioned non-impact printing head by replacing a printing wheel or drum for the platen described previously.

I claim:

1. Mechanism for moving a printing head in a printer having a frame, a head holder mounting thereon said printing head and movable between a start position and a terminal position in said frame, means cooperating with said printing head for the printing operation of a sheet interposed between said printing head and said cooperating means while said printing head is moving from said start position to said terminal position, control circuit means for supplying printing signals to said printing head in timed relationship to the movement of said head holder from said start position to said terminal position, an electric motor for driving said head electromagnetic clutch mounted on said frame and operably coupled with said motor so as to be driven thereby when said electromagnetic clutch is actuated, said electromagnetic clutch being connected to said control circuit means so as to be released upon receipt of a signal from said control circuit means, a winding drum rotatably mounted on said frame, a reduction gear means connecting said winding drum to said electromagnetic clutch so as to releasably drive said winding drum at a reduced speed with respect to that of said electromagnetic clutch, pulley means rotatably mounted on said frame, an endless wire stretched around said winding drum and said pulley means so as to be driven by said drum, said pulley means being so arranged that a portion of said wire stretched around said pulley means extends in parallel and close to the path of movement of said head holder over the length thereof, a point on said portion of said wire being secured to said head holder thereby permitting said holder to be moved toward said terminal position against the action of said spring means by said winding drum through said wire when said electromagnetic clutch is actuated, a detecting coil operably coupled with said electromagnetic clutch and connected to said control circuit means, said detecting coil being so arranged in timed relation to the actuation of said electromagnetic clutch as to generate said signal for releasing said electromagnetic clutch when said head holder is moved to said terminal position thereby permitting said head holder to be moved back toward said start position by the action of said spring means, and switch means connected to said control circuit means, said switch means being so positioned that the same is actuated when said head holder reaches said start position so as to actuate said electromagnetic clutch through said control circuit means.

2. Mechanism according to claim 1, further comprising normally closed switch means connected in series to said electromagnetic clutch and said control circuit means, said normally closed switch means being so located that the same abuts against said head holder when the same reaches said terminal position so as to be opened thereby so that said electromagnetic clutch false function of said control circuit means. 

1. Mechanism for moving a printing head in a printer having a frame, a head holder mounting thereon said printing head and movable between a start position and a terminal position in said frame, means cooperating with said printing head for the printing operation of a sheet interposed between said printing head and said cooperating means while said printing head is moving from said start position to said terminal position, control circuit means for supplying printing signals to said printing head in timed relationship to the movement of said head holder from said start position to said terminal position, an electric motor for driving said head holder, wherein the improvement comprises spring means connected at its one end to said head holder while the other end is connected to said frame so as to urge said head holder toward said start position, an electromagnetic clutch mounted on said frame and operably coupled with said motor so as to be driven thereby when said electromagnetic clutch is actuated, said electromagnetic clutch being connected to said control circuit means so as to be released upon receipt of a signal from said control circuit means, a winding drum rotatably mounted on said frame, a reduction gear means connecting said winding drum to said electromagnetic clutch so as to releasably drive said winding drum at a reduced speed with respect to that of said electromagnetic clutch, pulley means rotatably mounted on said frame, an endless wire stretched around said winding drum and said pulley means so as to be driven by said drum, said pulley means being so arranged that a portion of said wire stretched around said pulley means extends in parallel and close to the path of movement of said head holder over the length thereof, a point on said portion of said wire being secured to said head holder thereby permitting said holder to be moved toward said terminal position against the action of said spring means by said winding drum through said wire when said electromagnetic clutch is actuated, a detecting coil operably coupled with said electromagnetic clutch and connected to said control circuit means, said detecting coil being so arranged in timed relation to thE actuation of said electromagnetic clutch as to generate said signal for releasing said electromagnetic clutch when said head holder is moved to said terminal position thereby permitting said head holder to be moved back toward said start position by the action of said spring means, and switch means connected to said control circuit means, said switch means being so positioned that the same is actuated when said head holder reaches said start position so as to actuate said electromagnetic clutch through said control circuit means.
 2. Mechanism according to claim 1, further comprising normally closed switch means connected in series to said electromagnetic clutch and said control circuit means, said normally closed switch means being so located that the same abuts against said head holder when the same reaches said terminal position so as to be opened thereby so that said electromagnetic clutch is released to positively prevent said head holder from moving beyond said terminal position regardless of the false function of said control circuit means. 